1) The Calmness is a global combat attribute that starts from the value 5 (five) in turn 1.
2) In every following turn the value of the global Calmness decreases with 1. For example in turn 2 the value of the global Calmness will decrease to 5-1=4; in turn 3: 4-1=3 and so on.
3) In turn 6 the value of the global Calmness will get to be 0 (zero). And from that turn until the end of the battle its value will stay at 0 (zero).
4) Every card in the game has an attribute "specific card Calmness" with a specific value.
5) When the value of the specific card Calmness of a card is below the value of the Global Calmness in a concrete turn the card CANNOT be played (see Example 1)
6) Every card in the game which doesn't have a specified card Calmness (there is no Calmness icon with value on the card) has a specific card Calmness with value 5 (which means that it can be played every turn even in turn 1).
7) The purpose of the Calmness is to prevent the most powerful cards to be played from the very first turns and cripple the less lucky player who didn't draw good cards in the first turns.

Example 1:
Card A has a specific card Calmness A1=4. Card B has a specific card Calmness B1=2. Card C has not displayed icon with specified card Calmness and so has a "hidden" specific card Calmness C1=5.
Turn 1:
The Global Calmnes is 5;
Card A has specific card Calmness A1=4, which is below the Global Calmness (4<5), so Card A CANNOT be played.
Card B has specific card Calmness B1=2, which is below the Global Calmness (2<5), so Card B CANNOT be played.
Card C has specific card Calmness C1=5, which is equal to the Global Calmness (5=5), so Card C CAN be played.
Turn 2:
The Global Calmnes is 5-1=4;
Card A has specific card Calmness A1=4, which is equal to the Global Calmness (4=4), so Card A CAN be played.
Card B has specific card Calmness B1=2, which is below the Global Calmness (2<4), so Card B CANNOT be played.
Card C has specific card Calmness C1=5, which is above the Global Calmness (5>4), so Card C CAN be played.
Turn 3:
The Global Calmnes is 4-1=3;
Card A has specific card Calmness A1=4, which is above the Global Calmness (4>3), so Card A CAN be played.
Card B has specific card Calmness B1=2, which is below the Global Calmness (2<3), so Card B CANNOT be played.
Card C has specific card Calmness C1=5, which is above the Global Calmness (5>3), so Card C CAN be played.
Turn 4:
The Global Calmnes is 3-1=2;
Card A has specific card Calmness A1=4, which is above the Global Calmness (4>2), so Card A CAN be played.
Card B has specific card Calmness B1=2, which is equal to the Global Calmness (2=2), so Card B CAN be played.
Card C has specific card Calmness C1=5, which is above the Global Calmness (5>2), so Card C CAN be played.
From that turn 4 untill the end of the battle all the cards A, B and C will have specific card Calmness > of the Global Calmness (which will continue to decrease until it reach 0 and stays at 0) so each of them will be playable.